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> > However, it would please me (if it's not too deadly to implement) to
> > see functions allowed to return set!-able references:
>
> > (set! (my-prop) 17)
> > (my-prop) => 17
>
> Kawa supports this (for some primitive functions - I haven't decided
> yet how to define such functions in Scheme).
>
> Note that having functions "return set!-able references" is
> probably not the way to do it, since we want a normal call (not in a
> set! context) to return plain value, not a reference. Instead,
> we allow functions to have "attributes", and one attribute is a
> functions setter function. Then we define:
> (set! (f . args) value)
> as being syntactic sugar for:
> ((setter f) value . args)
>
> > (While I'm at it, I'd argue for (set! (array-ref a 6) 'zork) etc. as a
> > clean alternative to setf.)
>
> The advantage of this design is that it is procedural, while
> setf is macro-based. Hence setf only works for setter functions
> explicitly known (by name) at compile time, but setter works on
> procedure *values* at run-time, and is therefore much more in
> the spirit of Scheme.
I'd propose to look at EuLisp which has this functionality:
(setter car) -> set-car!
so one uses:
(set l '(1 2 3 4))
(car l) -> 1
((setter car) l 5) -> '(5 2 3 4)
The setter for a function can be set using:
((setter setter) car set-car!)
--
Wolfgang Kechel
Email: wolfgang@prs.de
Patzschke + Rasp GmbH Bierstadter Str. 7 D-65189 Wiesbaden
Phone: +49-611-1731-26 FAX: +49-611-1731-31